This is why we store backups offline. If they are connected to the computer, then corruption (accidental or deliberate) can occur. For my backups, I keep a bunch of 2TB hard drives that I can stick into an eSata docking bay, backup my stuff, unmount the drive, and take it offline. It is then inaccessible by other stuff, including malware. I do this with my system drive as well. I have been able to restore my system to a known good state that way after getting pwnd or some other catastrophic event has occurred. IE, backup system drive, backup data, take backup drive offline. Make data system and data backups on a regular basis. When you have to restore the system and data, you may lose a bit of work, but mostly you will be intact.

As far as I understood, you have kept your back up file on your computer. That's not reasonable. If you have only one copy and it is corrupted, I guess chances are few to recover the information. I've been using Acronis Back up and Recovery tool(http://www.acronis.com/en-eu/cloud/backup/) and keep my back ups in the cloud. Very convenient since I can access them any time from any place.